Function position_to_char_offset

src/util.rs:731–764

Convert an LSP `Position` (line/character) to a character offset into a pre-built char array. Returns `None` when the position is beyond the end of `chars`. Handles UTF-16 column widths, end-of-line clamping, and trailing content without a newline.

(chars: &[char], position: Position)

/// Handles UTF-16 column widths, end-of-line clamping, and trailing
/// content without a newline.
pub fn position_to_char_offset(chars: &[char], position: Position) -> Option<usize> {
    let target_line = position.line as usize;
    let target_col = position.character as usize;
    let mut line = 0usize;
    let mut col = 0usize;

    for (i, &ch) in chars.iter().enumerate() {
        if line == target_line && col == target_col {
            return Some(i);
        }
        if ch == '\n' {
            // If we're at the target line and the target column is at or
            // past the end of the line, clamp to end-of-line.
            if line == target_line {
                return Some(i);
            }
            line += 1;
            col = 0;
        } else {
            col += ch.len_utf16();
        }
    }

    // Cursor at very end of content
    if line == target_line && col == target_col {
        return Some(chars.len());
    }
    // Target column past end of last line (no trailing newline)
    if line == target_line {
        return Some(chars.len());
    }

    None
}

/// Find which class the cursor (byte offset) is inside.
///